Sunday, April 9, 2017

I thought of Mercury going retrograde as I drove down a street in the "Avenues" district of Salt Lake City. The sun was setting a brilliant orange back-lighting the capitol and reflecting across the Great Salt Lake itself. Behind me a moon rose that was all but (an app on my iPhone would tell me it was 1 day and 3 hours away from) full.

For a the briefest of moments I was more aware than is possible of this careening spinning crazy ride through the gravity wells of curved spacetime that all the inhabitants of earth share in, and it was amazing, and then that moment was followed by another. I liked that one and followed it with a few more and then I was driving alongside I-80 and the surface of the Great Salt Lake was a mirror reflecting an gigantic ball of nuclear fire a million times larger than the planet I was driving across the surface of (Sun's volume is 1.4X10E18 km^3, and the Earth's volume is 1X10E12 km^3) and I liked it till the sun disappeared behind a range of snow covered mountains and the sky became dark enough to see the stars. And stars are really cool.

Perhaps it was the great weekend that had left me with the feeling that I was soaring through a universe that wanted to act like I was noticing it in new and thrilling ways?

Supposedly cell phones are going to glitch (more than normal) and other technology and communications are going to go awry. Some well meaning people recommend just curling up and cocooning as the “crazy” caused by Mercury’s retrograde passes.

I can only imagine that the wonderful full moon contributes to the mystical happenings.

“Gala Darling” describes some of the effects of Mercury going retrograde as “It’s like everyone you know has suddenly gone mad! You might find yourself getting into bizarre arguments about nothing at all, being unable to finish sentences or barely even able to form a coherent thought.” Imagine the effect on people who regularly lack the desire or ability to form coherent thoughts?!?

So, what makes this madness happen?

Mercury orbits the sun every 88 days, and it is common knowledge that the Earth orbits the sun every 365.25 days. This means that every Earth year mercury laps the Earth around the sun slightly more than four times.

Mercury orbits the sun the fastest of all the planets. As one travels out from the sun the planetary orbits become longer and longer. Venus orbits the sun every 225 days, and so it laps the earth every other year; sometimes twice in a year.

The planets farther from the sun than earth are lapped by the earth. Saturn orbits the earth only once every 29 years so the earth laps it almost every year.

To the casual observer the planets appear like slightly brighter specks of light against a scattering of bright specs of light in the night sky. They do not appear to be billions of times closer. We can deduce that they are closer because the angle we see them at changes as we move around the sun, and we move around the sun at an incredibly high rate of speed (30 km/s) so even though the planets are far away they can appear to be in different places almost every night. Because the orbits are roundish the planets will appear back at almost their starting place after some multiple of the ratio of the two orbit durations. Ancient astronomers used to squint up at the night sky and make surprisingly accurate predictions of the orbit times for all the planets they could see by measuring things like how long it took them to pass back through some particular constellation.

The geometry that defines the retrograde motion is not difficult, but it is cumbersome to the point of being tedious. I will spare you this time. Even more complex is the model Ptolemy used to describe the motions of the planets given a geocentric model of the solar system. The model includes orbits looping about orbits and the complete trace is much like something one could create with a Spirograph set. I always loved Spirograph so it is unfortunate that the model apparently fails after a while. That is one of the problems with overly complex models; they hide failures in late iterations.

I saw at least one YouTube video created with the intensity of a WTC7 conspiracy theorist about how retrograde motion in Mercury proves that the Sun orbits the Earth. I am sure the government is hiding this from us because we re all some sort of “sheeple”, but I did not watch it that long.

Because the planets are all traveling in the same direction about the sun they mostly appear to travel in the same direction across the night sky. Venus and Mercury, being on the sun side of the earth most of the time, do not really travel across the night sky, but the little they can be observed to move they go in one direction mostly. Because all the planets either lap or are lapped by the Earth this apparent motion across the sky also changes direction for short (relative to the orbit of the earth) period of time. That change in direction is called apparent retrograde motion, or in astrology terms “being in retrograde”.

Wikepedia has a great picture that shows the apparent retrograde motion to an observer on earth of an outer planet.

I tried to do something similar for Mercury, but, the changes in angle are so big it is hard to contain them in a graphic. Here is one picture I made which has the Earth going about a quarter of the way around the sun and Mercury going all the way around the sun. I’ve numbered where the parallax puts the apparent location of Mercury against the backdrop of apparently unmoving stars.

If you look you can see how the order of the numbered observations changes between observations 2 and 3, then goes in back in the same direction for the sequence of observations 3,4, and 5. The retrograde motion would occur between observations 2 and 3. One of the other things this picture make kind of obvious is that most of the observations occur during daytime on Earth when Mercury is not visible to the naked eye.

In this picture I’ve tried to capture observations occurring at a great enough angle as to have Mercury at least visible in the late evening or just around dawn. Unfortunately when I do this the graphic does not capture any retrograde motion. The point being that it is really hard to notice retrograde motion in mercury, even though it happens at a greater frequency than it does for any of the other planets. In fact this problem with Mercury being obscured by daylight is one of the reasons why it is suggested that the great astronomer Kepler did not ever observe Mercury during his life; let alone observe its retrograde motion.

So those that put stock in the magical meaning of Mercury being “in retrograde” are almost forced to use the calculations and data derived by processes all to rational and specific to make room for the ephemeral magic mumbo jumbo they use them to define.

Mercury will also be retrograde August 13th through September 5th so it will be retrograde during the solar eclipse; I wonder what kind of special magic that will cause?

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About Me

I am an adult onset atheist. I cannot blame parents, society, or an unhappy childhood on my decision to abandon all things theist. I clung for a while to a deist god, but it too was eventually thrown onto the trash-heap. Why insist that I am believing in a “god” when “gravity” or “electromagnetic radiation” are better names? I finally found that I was clinging to the weakest shadow of a deist god because I connected the belief in this imaginary entity with so many good things in the world. One day I realized that those good things would be better without the residue of a belief in god contaminating them.